The use of economic sanctions to stem weapons proliferation acquired a new dimension in the 1990s. While earlier legislation required the cutoff of foreign aid to countries engaged in specified nuclear proliferation activities and mentioned other sanctions as a possible mechanism for bringing countries into compliance with goals of treaties or international agreements, it was not until 1990 that Congress enacted explicit guidelines for trade sanctions related to missile proliferation. In that year a requirement for the President to impose sanctions against U.S. persons or foreign persons engaging in trade of items or technology listed in the Missile Technology Control Regime Annex (MTCR Annex) was added to the Arms Export Control Act and to the Export Administration Act of 1979. Subsequently, Congress legislated economic sanctions against countries that contribute to the proliferation of chemical, biological, and nuclear weapons in a broad array of laws.